The present invention relates to an apparatus and method for supplying fuel in an internal combustion engine with a variable valve lifter, preferably usable in an automobile.
A prior art internal combustion engine as disclosed by JP-A-2002-97916 includes a variable valve lifter by which lifter a lifted distance and/or a lift timing of an air intake valve is adjusted in accordance with an operating condition of the engine so that a mileage under low-load operation and an output power under high-load operation are improved.
An object of the present invention is to provide an apparatus and method for supplying fuel in an internal combustion engine with a variable valve lifter, by which apparatus and method unburned carbon hydride is restrained from being exhausted from the internal combustion engine.
An apparatus for supplying fuel in an internal combustion engine including a combustion chamber, an air intake valve for selectively allowing an air and the fuel through the air intake valve to flow into the combustion chamber, and a variable valve lifter for adjusting an opening degree of the air intake valve with respect to the combustion chamber at each of combustion cycles, according to the present invention, comprises a vaporizing speed adjuster for changing a vaporizing (vaporization or vaporized fuel increasing) speed of the supplied fuel in accordance with a control signal to adjust a degree of vaporization of the fuel passing the air intake valve, and a controller for generating the control signal for changing the degree of vaporization of the fuel in accordance with at least one of the opening degree of the air intake valve and a load to be borne by the internal combustion engine (that is, an output torque or power to be output by the internal combustion) engine to restrain the fuel of liquid state from existing in the combustion chamber.
Since the vaporizing (vaporization or vaporized fuel increasing) speed of the supplied fuel is changed to adjust the degree of vaporization (for example, mass flow rate % of the vaporized fuel with respect to the whole mass flow rate of the supplied fuel) of the fuel passing the air intake valve so that the fuel of liquid state is restrained from existing in the combustion chamber, unburned carbon hydride generated from the fuel of liquid state existing in the combustion chamber is restrained from being exhausted from the internal combustion engine without unnecessary energy consumption for vaporizing always the fuel and/or vaporizing the whole of the fuel.
A method for supplying fuel in an internal combustion engine including a combustion chamber, an air intake valve for selectively allowing an air and the fuel to flow through the air intake valve into the combustion chamber, and a variable valve lifter for adjusting an opening degree of the air intake valve with respect to the combustion chamber at each of combustion cycles, according to the present invention, comprises the steps of: generating a control signal for changing a degree of vaporization of the fuel passing the air intake valve in accordance with at least one of the opening degree of the air intake valve and a load (for example, an output torque or power) of the internal combustion engine to restrain the fuel of liquid state from existing in the combustion chamber, and changing a vaporizing (vaporization increasing) speed of the supplied fuel in accordance with the control signal to adjust the degree of vaporization of the fuel.
Since the vaporizing (vaporization or vaporized fuel increasing) speed of the supplied fuel is changed to adjust the degree of vaporization (for example, mass flow rate % of the vaporized fuel with respect to the whole mass flow rate of the supplied fuel) of the fuel passing the air intake valve so that the fuel of liquid state is restrained from existing in the combustion chamber, unburned carbon hydride generated from the fuel of liquid state existing in the combustion chamber is restrained from being exhausted from the internal combustion engine without unnecessary energy consumption for vaporizing always the fuel and/or vaporizing the whole of the fuel.
If the control signal is generated in such a manner that the vaporizing speed of the fuel is increased in accordance with (for example, in proportion to) decrease of the opening degree of the air intake valve and/or the load, the unnecessary energy consumption is effectively decreased. If the control signal is generated in such a manner that the vaporizing speed of the fuel obtainable when the opening degree of the air intake valve and/or the load is not more than a predetermined value is higher than the vaporizing speed of the fuel obtainable when the opening degree of the air intake valve and/or the load is more than the predetermined value, an adjustment of the vaporizing speed of the fuel is easily performed by only switching on and off the acceleration of the vaporization of the fuel.
The vaporizing speed adjuster may include a heater to heat the supplied fuel so that the vaporization of the fuel is accelerated by thermal energy to increase the degree of vaporization of the fuel. The vaporizing speed of the supplied fuel may be changeable in accordance with a variation of the heating thermal energy quantity. The vaporizing speed adjuster may include an air injector to inject an air into the fuel so that the vaporization of the fuel is accelerated by collision between the fuel and the injected air (for forming fuel fine mist to decrease diameter of the mist particles so that a ratio of surface area of particle to mass of particle is increased to accelerate the vaporization of the fuel) to increase the degree of vaporization of the fuel. The vaporizing speed of the supplied fuel may be changeable in accordance with a mass flow rate of the injected air.
The vaporizing speed adjuster may include a fuel injector to change a timing of fuel injection with respect to a pressure in the combustion chamber in accordance with the control signal, and the control signal is generated in such a manner that the pressure in the combustion chamber obtainable when the fuel is injected by the fuel injector lowers in accordance with a decrease of the opening degree of the air intake valve and/or the load so that the vaporization of the fuel is accelerated by a difference in pressure across (between upstream and downstream sides of) the air intake valve (increasing in accordance with decrease of the pressure in the combustion chamber) to increase the degree of vaporization of the fuel by stirring a mixture of the air and fuel with a high velocity of the mixture over the air intake valve and/or collision between the air and fuel for forming the fine particle fuel mist. If the fuel is injected with the pressure in the combustion chamber less than a predetermined degree and is prevented from being injected with the pressure in the combustion chamber not less than the predetermined degree, the stirring of the mixture of the air and fuel with the high velocity of the mixture over the air intake valve and/or collision between the air and fuel for forming the fine particle fuel mist is securely performed, by keeping the difference in pressure across the air intake valve more than a desirable degree. It is preferable for keeping the difference in pressure across the air intake valve more than the desirable degree that a pressure at an upstream side of the air intake valve in a fuel flow direction is higher than the pressure in the combustion chamber when the pressure in the combustion chamber is less than the predetermined degree. If the fuel is injected with the pressure in the combustion chamber less than the predetermined degree and is prevented from being injected with the pressure in the combustion chamber not less than the predetermined degree when the opening degree of the air intake valve and/or the load is not more than a predetermined value, the fuel may be injected with the pressure in the combustion chamber not less than the predetermined degree when the opening degree of the air intake valve and/or the load is more than the predetermined value, so that a large flow rate of the fuel at each combustion cycle can be supplied by a long time period (for example, including a part of an exhaust piston stroke time period) of the fuel injection to increase an output power of the engine when the opening degree of the air intake valve and/or the load is more than the predetermined value.
If the vaporizing speed adjuster includes the fuel injector to change a timing of fuel injection in accordance with the control signal, and when the opening degree of the air intake valve and/or the load is not more than a predetermined value, the fuel is injected during a flow of the air into the combustion chamber through the air intake valve and is prevented from being injected during a flow of an exhaust gas out of the combustion chamber, since the pressure in the combustion chamber during the flow of the air into the combustion chamber through the air intake valve, that is, the air intake piston stroke is lower than the pressure in the combustion chamber during the flow of the exhaust gas out of the combustion chamber through the air intake valve, that is, the exhaust piston stroke, the difference in pressure across the air intake valve (increasing in accordance with decrease of the pressure in the combustion chamber) is kept sufficiently large for increasing the degree of vaporization of the fuel by stirring the mixture of the air and fuel with the high velocity of the mixture over the air intake valve and/or collision between the air and fuel for forming the fine particle fuel mist.
The vaporizing speed adjuster may include a first fuel supply path capable of supplying a fuel of relatively high vaporization degree and a second fuel supply path capable of supplying a fuel of relatively low vaporization degree while the control signal is generated to change a ratio between a fuel flow rate through the first fuel supply path and a fuel flow rate through the second fuel supply path so that the vaporizing speed of the fuel is changed in accordance with the ratio.
The opening degree of the air intake valve may be a maximum opening degree of the air intake valve at each of the combustion cycles or a maximum distance of a movable valve body of the air intake valve at each of the combustion cycles from a shut-off position of the movable valve body thereof. It is preferable for restraining a film of the fuel from being formed on the air intake valve and the fuel of liquid state from being moved into the combustion chamber from the air intake valve that the vaporizing speed adjuster is arranged at an upstream side of the air intake valve in a fuel flow direction. The thermal energy of the heater may be obtained from at least one of electric power, a coolant of the combustion engine and an exhaust gas flowing out of the combustion chamber.
The opening degree of the air intake valve may be changed in accordance with a change of at least one of an output power and an output torque to be output by the engine, that is, a load to be borne by the combustion engine, for example, the greater the at least one of the output power and the output torque of the combustion engine to be output is, the greater the opening degree of the air intake valve is. When the opening degree of the air intake valve is changed in accordance with the change of the at least one of the output power and the output torque to be output by the engine, that is, the load to be borne by the combustion engine, the vaporizing (vaporization or vaporized fuel increasing) speed of the supplied fuel may be changed in accordance with the at least one of the output power and the output torque to be output by the engine, that is, the load to be borne by the combustion engine, instead of the opening degree of the air intake valve.
The vaporizing speed adjuster may include a vibrator to vibrate the fuel so that the vaporization of the fuel is accelerated by atomizing the fuel with vibrating the fuel to increase the degree of vaporization of the fuel by accelerating the vaporization of the supplied fuel.
According to the present invention, an apparatus for supplying fuel in an internal combustion engine including a combustion chamber, and an air intake valve for selectively allowing an air and the fuel through the air intake valve to flow into the combustion chamber, comprises a fuel supplier for supplying the fuel to an upstream side of the air intake valve, a vaporizing accelerator for at least one of vaporizing and atomizing in accordance with a control signal the fuel supplied by the fuel supplier, and a controller for generating the control signal for adjusting the at least one of vaporization and atomization of the fuel in accordance with a condition of the internal combustion engine. The condition of the internal combustion engine may be a load of the internal combustion engine or a maximum distance of a movable valve body of the air intake valve at each of the combustion cycles from a shut-off position of the movable valve body thereof while the maximum distance of the movable valve body is changeable in accordance with the load of the internal combustion engine. The fuel supplier may be a fuel injector. The vaporizing accelerator may include a heater, an atomizer or an air flow supplier for atomizing the fuel.
According to the present invention, a method for supplying fuel in an internal combustion engine including a combustion chamber, and an air intake valve for selectively allowing an air and the fuel to flow through the air intake valve into the combustion chamber, comprises the steps of: generating a control signal in such a manner that performance of at least one of vaporization and atomization of the fuel increases in accordance with a decrease in load of the internal combustion engine, and changing the performance of the at least one of vaporization and atomization of the fuel in accordance with the control signal. A maximum distance of a movable valve body of the air intake valve at each of the combustion cycles from a shut-off position of the movable valve body thereof may increase in accordance with an increase in load of the internal combustion engine.
Other objects, features and advantages of the invention will become apparent from the following description of the embodiments of the invention taken in conjunction with the accompanying drawings.